Tuesday, March 4, 2014

Untangling multiple fauna millions of years apart at the same site

Newly identified dinosaur fauna sheds light on evolution

It’s not a surprise that researchers
originally assumed that everything that was turning up was effectively part of
the same series of fossil beds. After all, such things were extraordinarily
rare, and basically everything was preserved in volcanic ash. What were the
odds that this was more than one fauna that just happened to overlap exactly
geographically and in preservation type? The fact that many of the early
discoveries were made by farmers or came through fossil dealers added to the
confusion. Without knowing the exact origins of the material it was impossible
to correlate the various fossil beds and outcrops that spread from the Chinese region
of Inner Mongolia though the province of Liaoning and even into North Korea

However, in recent years it has become increasingly
apparent that some of the material was rather older than had previously been
thought. The new paper (of which I am an author) reviews the evidence establishing
the geological age of these older fossils, and more importantly, suggests that
they can be considered part of a new fauna. These older specimens come from a
number of different localities, but they can be linked together by the presence
of a salamander
species. Radiometric dating work for numerous sites confirms an
age of around 160m years old. We can thus use this species as a marker
to help define what does and does not fall into this fauna and the dating
suggests the existence of these animals over a relatively limited period of geological
time.